1 - it doesn't make her look better for me
2 - having secrets is not necessarily evil. Sometimes it can be explained as : "I want to protect by partner." There are also other possibilities.
3 -I probably missed one story then. Can You show me issue in which we learned that Gambit doesn't have secrets?
If I would write this I would say: "You are completly right."
My point is:
Gambit has secrets.
When Rogue absorbs his memories ... then she is acting more like Gambit (their first kiss for example).
Rogue having secrets shouldn't be surprising.